Fiber reinforced composite shaft with metallic connector sleeves mounted by longitudinal groove interlock

ABSTRACT

A tubular fiber reinforced composite shaft is formed (as described) which integrally incorporates a metal sleeve or connection at the end thereof. Initially a metal sleeve having circumferentially spaced recesses on the outer periphery thereof is positioned upon a segment of a mandrel. Fibrous material bearing a non-solidified resinous material is applied around the mandrel and around the recesses in the sleeve. Portions of the previously applied fibrous material bearing the non-solidified resinous material are pressed into the recesses. Additional fibrous material bearing the non-solidified resinous material is applied to the previously applied fibrous material. The resinous material next is solidified to form a tubular composite shaft whereby a secure torsion-transmitting connection is made with the sleeve, and the mandrel is removed.

BACKGROUND AND OBJECTS OF THE INVENTION

This invention relates to fiber reinforced composite shafts and, moreespecially, to vehicle drive shafts comprising a fiber reinforcedresinous shaft body with metallic coupling sleeves mounted at the endsthereof.

Tubular fiber reinforced composites have been heretofore proposed, asdemonstrated by U.S. Pat. Nos. 2,882,072 issued to Noland on Apr. 14,1959, and 3,661,670 issued to Pierpont on May 9, 1972. In the Pierpontpatent, for example, it has been proposed to form such composites from aresinous material which is reinforced by glass fibers. In particular,filaments bearing a non-hardened resinous material (i.e., an uncuredthermosetting resin) are wound around a mandrel until the desiredthickness has been established. The reinforcing fibers can be positionedwithin the wall of the tubular composite in varying angularrelationships. Thereafter, the resinous material is solidified (i.e. iscured). A premolded threaded end portion can be mounted at the ends ofthe tubular composite, such as by the winding of filaments directlyaround the end portion during the winding process.

It recently has been proposed to form vehicle drive shafts from tubularfiber reinforced composites, as demonstrated by U.S. Pat. No. 4,041,599issued to Smith on Aug. 16, 1977, and published Japanese Application No.52-127542, entitled "Carbon Fiber Drive Shaft" which claims priority forthe filing of U.S. Ser. No. 676,856 on Apr. 14, 1976 of Gordon PeterMorgan, now U.S. Pat. No. 4,089,190 issued May 16, 1978. In the Japaneseapplication filaments bearing a non-hardened resinous material (e.g., anuncured thermosetting resin) are wound around a mandrel until thedesired thickness has been established, whereupon the resinous materialis cured. Zones or layers are positioned circumferentially within thewall of the shaft in the specific angular relationships there disclosed.

The above-mentioned Smith patent proposes the attachment of a carbonfiber reinforced epoxy drive shaft directly to a universal jointextension by a specific bonding technique.

Fiber reinforced composite shafts exhibit advantages over metallicshafts, i.e., they are lighter in weight, more resistant to corrosion,stronger, and more inert.

In copending application Ser. No. 890,230 filed concurrently herewith,of Derek N. Yates and David B. Rezin entitled "Improved Carbon FiberReinforced Composite Drive Shaft", a fiber reinforced composite driveshaft is disclosed which exhibits improved service characteristics andthe necessary strength and durability to withstand the various stressesencountered during vehicle operation. The disclosure of that copendingapplication is herein incorporated by reference as if set forth atlength.

Since direct welding or bonding of a resin shaft to metal does notnormally create a sufficiently strong and durable connection on aconsistent and reliable basis, the use of metallic connector sleevesmounted at the ends of the shaft in accordance with the concept of thepresent invention provides a means for accomplishing a secure weldedconnection similar to that utilized with conventional metallic shafts.

The high torque loads which are to be transmitted by a vehicle driveshaft require that an extremely strong and durable torsional driveconnection be established between the sleeves and shaft body. Previousproposals for mounting sleeves by employing adhesives or by wrapping thefilament bundles around circumferential grooves on the sleeve periphery,cannot be relied upon to provide a connection of the requisite strengthand durability.

It is, therefore, an object of the present invention to provide a novel,fiber reinforced resin shaft which minimizes or obviates problems of thetypes discussed above.

It is an additional object of the invention to provide a novel, fiberreinforced resin shaft suitable for use as a drive shaft in a vehiclepower train.

It is a further object of the invention to provide novel methods andapparatus for securing metal connector sleeves to the ends of fiberreinforced resin shafts to enable the shafts to transmit high torsionalloads.

BRIEF SUMMARY OF PREFERRED EMBODIMENTS OF THE INVENTION

These objects are achieved by the present invention wherein a metalsleeve having circumferentially spaced recesses upon the outer peripherythereof is positioned upon a segment of a mandrel. Fibrous materialbearing a non-solidified resinous material is applied to the mandrel andover the recesses in the sleeve. Portions of the applied fibrousmaterial are pressed into the recesses while bearing the non-solidifiedresinous material. Additional fibrous material bearing thenon-solidified resinous material is applied to the previously appliedresinous material. The resinous material is solidified with portions ofthe previously applied fibrous material positioned in the recesses tocreate a torsion-transmitting connection therebetween. Thereafter, themandrel is removed.

THE DRAWING

Other objects and advantages of the present invention will becomeapparent from the subsequent detailed description of a preferredembodiment thereof in connection with the accompanying drawings in whichlike numerals designate like elements, and in which:

FIG. 1 is a side view of an end of a composite shaft formed inaccordance with the present invention;

FIG. 2 is a cross-sectional view of the shaft, taken along line 2--2 inFIG. 1;

FIG. 3 is an enlarged, fragmentary view of the cross-sectional showingof FIG. 2;

FIG. 4 is a fragmentary, longitudinal sectional view of a connectorsleeve in accordance with the present invention;

FIG. 5 is a cross-sectional view of the connector sleeve, taken alongline 5--5 in FIG. 4;

FIG. 6 is an end view of a tongue-carrying segment forming part of theshaft of the present invention;

FIG. 7 is a longitudinal sectional view of a segment, taken along line7--7 of FIG. 6;

FIG. 8 is a fragmentary, longitudinal sectional view of a shaftaccording to the present invention, taken along line 8--8 of FIG. 2;

FIG. 9 is a view similar to FIG. 8 taken along line 9--9 of FIG. 2;

FIG. 10 is a fragmentary longitudinal sectional view taken during anintermediate step of shaft fabrication depicting a segment beingretained by a clamp;

FIGS. 11-15 are views corresponding to FIGS. 1, 2, 3, 8, and 9 of analternate embodiment of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

A shaft 10 according to the present invention includes a fiberreinforced composite shaft body 12 of cylindrical cross-section, and ametal connector sleeve 14 secured preferably at each end of the shaftbody.

The connector sleeve 14 is generally cylindrical and formed of anappropriate metal, such as steel or aluminum for example. The sleeveincludes an inner annular surface 16 of constant diameter which issubstantially contiguous with an inner surface 18 of the shaft bodylocated longitudinally inwardly thereof, as is evident from FIG. 8.

The outer surface of the sleeve includes circumferentially spacedrecesses. Preferably, there are provided longitudinally extending,circumferentially spaced grooves 20 (FIGS. 4, 5) which extend from aninner end 22 of the sleeve and terminate short of the outer end 24thereof. If desired, the grooves 20 could extend the entire length ofthe sleeve. The depth of each groove increases as the longitudinallyinner end 22 of the sleeve is approached. Radially outer edges 23 of thegrooves form relatively sharp corners (FIG. 5).

The grooves 20 are defined by circumferentially spaced, radiallyprojecting ribs 25 which increase in depth or thickness as thelongitudinally inner end 22 of the sleeve is approached, thereby forminginclined faces 27 which face generally longitudinally and radiallyoutwardly.

The inner end 22 of the sleeve 14 is tapered both longitudinally andradially inwardly at 26 to provide a feather edge 28 for the receptionof windings of reinforced resin material as will be discussed.

During fabrication of a preferred form of the shaft, a pair of connectorsleeves are positioned on a mandrel in longitudinally spacedrelationship. The sleeves engage the mandrel somewhat snugly, butloosely enough to be removable therefrom. An appropriate clampingarrangement holds the sleeves in place. The mandrel is coated with arelease substance to resist the adherence thereto of resin or adhesives.Thereafter, the shaft body 12 is formed around both the mandrel andsleeve.

Construction of the shaft body 12 is preferably performed in a mannermore fully described in the aforementioned application of Yates andRezin. Summarized briefly, layers of fiber reinforced resin-impregnatedmaterial are applied, prefably in the form of bundles of substantiallyparallel continuous filaments bearing a non-solidified (i.e., liquid,soft and tacky, or molten) resinous material. The bundles can be dippedin an uncured liquid thermosetting resin, such as an epoxy resin, andthen wound around the mandrel in multiple passes until a layer ofdesired thickness is established. Attention is further directed to U.S.Pat. Nos. 3,661,670, 3,202,560, and 3,231,442 for additional detailsconcerning possible arrangements for the clamping of sleeves and windingof filament bundles. The disclosures of these patents are incorporatedherein by reference as if set forth at length.

The term "layer" as used herein specifies a circumferential zone withinthe wall of the tubular drive shaft wherein the fibrous reinforcement isdisposed in a specific configuration and differs from the adjacentzone(s) with respect to the configuration and/or composition of thefibrous reinforcement. A single layer may include a multiple passalignment or buildup of fibrous reinforcement in a given configuration.The term layer encompasses an alignment wherein the fibrousreinforcement is disposed therein at both plus and minus a given anglewhich optionally can be builtup in multiple passes.

The fibers reinforce the thermoset resin matrix to impart necessaryproperties of strength and durability to the shaft. In this regard,glass fibers (e.g., E-glass or S-glass) and carbon fibers (i.e., eitheramorphous or graphitic) materials are preferred. The carbon fiberscommonly contain at least 90 percent carbon by weight, and preferably atleast 95 percent carbon by weight. Additionally preferred carbon fibershave a Young's modulus of elasticity of at least 25 million psi (e.g.,approximately 30 to 60 million psi).

The plies of filament bundles are wound in various orientation relativeto the longitudinal axis of the drive shaft, and can be built-up todifferent thicknesses, respectively. Preferably, an initial layer ofglass fibers is applied at an angle of from ±30° to ±50° relative to aline parallel to the longitudinal axis of the shaft. Next, a layer ofglass fibers is applied at an angle of from 0° to ±15°. Thereafter, alayer of carbon fibers is applied at an angle of from 0° to ±15°. Then alayer of glass fibers is applied at about an angle of from about ±60° to90°.

Of course the number and composition of layers, as well as theirorientation and thickness may vary, depending upon the characteristicsdesired to be imparted to the shaft.

Rather than utilizing filament winding (e.g., wet winding or prepregwinding), other tube forming procedures can be employed, such as tuberolling, tape wrapping, or pultrusion, for example. In the former step,comparatively wide sections of resin impregnated tape are precut topatterns, stacked in sequence, and rolled onto the mandrel.

After the layers have been applied, the non-solidified resin is cured.In this regard, the resin may be of a self-curing type, or may be of akind which cures in response to being subjected to heat and/or a curingagent.

Relating more particularly to the present invention, after a pair ofsleeves 14 have been properly positioned on a mandrel 15, an initiallayer 30 of glass fibers is wound around the mandrel and sleeves atabout a ±45 degree angle. This layer terminates short of the outermostend of the sleeve, so that the outer portion 24 of the sleeve remainsexposed. The grooves 20 are circumferentially covered by this layer 30.

The filament bundles are preferably wound more loosely around the sleevethan around the mandrel to facilitate entry of the layer 30 into thegrooves 20 as will be discussed.

A plurality of arc-shaped metal segments 32 (FIG. 6) are positionedaround the circumference of the shaft. These segments, preferably formedof steel, include radially inwardly projecting, longitudinally extendingtongues 34 which overlie the grooves 20. Wall portions 33 between thetongues are of diminishing thickness toward a longitudinally inner endof the segment to conform to the tapering ribs 25 of the sleeve 14.Sides 36 of the tongues extend at an angle relative to the radialdirection so as to be convergent toward an imaginary point which liesbetween an inner face 38 of the tongue and the center of revolution ofthe segment 32.

The segments 32 are held in place on the sleeve in any suitable fashion,such as by one or more clamps 35 (FIG. 10) which extendcircumferentially around the shaft and segments. In this fashion, thetongues 34 push portions of the layer 30 into the grooves 20 (FIG. 3).

Thereafter, a layer 39 of glass fibers is wound around the layer 30 andthe segments 32 at about a zero degree angle. As this windingprogressively covers the segments 34 (FIG. 10), the clamp or clamps 35are removed. When the winding has been completed, the layer 39 willcover the segments to hold them firmly in position.

Next, a layer 40 of graphite fibers is wound around the layer 39 atabout a zero degree angle.

Finally, a layer 42 of glass fibers is wound at about a 90 degree anglearound the layer 40.

Thereafter, the non-solidified resin is cured to bond the layerstogether to form an integral composite, and the shaft is removed fromthe mandrel.

It will be understood that any number of layers can be applied and atvarious angles and thicknesses, depending upon desired shaftcharacteristics.

It will be appreciated that the above-described winding technique servesto mechanically lock shaft body 12 and sleeve 14 together. Longitudinalmovement of the sleeve 14 in a longitudinally outward direction isprevented by engagement between the fiber layers and the inclinedsurfaces 27 of the ribs 25. Longitudinally inward movement of the sleeve14 is prevented by engagement between the tapered surface 26 and thefiber layers. The sleeve and shaft body 12 are capable of transmittinghigh torque loadings therebetween. That is, the presence of portions ofthe layer 30 within the grooves 20 prevents relative rotationtherebetween. The corners 23 of the grooves 20 which contact the layer30 are relatively sharp, thereby effectively resisting the occurrence ofrelative slippage between the shaft body and sleeve. Dislodgement of thelayer 30 from the grooves 20 is prevented by the metal segments 32, thelatter being embedded within the fiber windings to form a permanent,integral part of the shaft.

The sleeves 14 facilitate connection of the shaft to metal componentssuch as metal yokes in a vehicle power train, since directmetal-to-metal welding contact is possible.

Although not necessary, it might be desirable to apply an adhesivebetween the sleeve 14 and initial layer 30 to augment the connectiontherebetween.

In an alternative embodiment of the invention, depicted in FIGS. 11-15,the layers 30 and 39 are applied prior to emplacement of metal segments50. These segments 50 include tongues 52 which constitute deformedportions of the segments. In this fashion, a recess 54 is formed on theouter surface of the segments. After the segments 50 are positionedaround the layer 39, shims 56 are positioned in the recesses 54 so thatthe outer circumference defined by the segments is smooth and unbroken.The tongues 52 deform both layers 30, 39 inwardly such that portions ofthe layer 30 enter the grooves 20 and portions of the layer 39 enterresulting grooves formed in the layer 30. Thereafter, the layers 40 and42 are applied.

Although the mechanical lock concept of the present invention isdisclosed in conjunction with a particular shaft body, it is to beunderstood that this concept has utility with composite shafts ingeneral wherein fibrous reinforcement is present in a resinous matrixmaterial.

Although the invention has been described in connection with a preferredembodiment thereof, it will be appreciated by those skilled in the artthat additions, modifications substitutions and deletions notspecifically described may be made without departing from the spirit andscope of the invention as defined in the appended claims.

We claim:
 1. A method of forming a tubular fiber reinforced compositeshaft comprising the steps of:positioning a metal sleeve havingcircumferentially spaced recesses upon the outer periphery thereof upona segment of a mandrel, said recesses each having a dimension in thelongitudinal direction; applying fibrous material bearing anon-solidified resinous material upon said mandrel and over saidrecesses in said sleeve; arranging a plurality of pressing members inradially inwardly pressing relationship with said previously appliedfibrous material and in overlying relationship with said recesses topress portions of said previously applied fibrous material into saidrecesses while bearing said non-solidified resinous material thereon;applying additional fibrous material bearing said non-solidifiedresinous material to said previously applied fibrous material and aroundsaid pressing members; solidifying said resinous material with thepressed portions of said previously applied fibrous material beingpositioned in said recesses to create a torsion-transmitting connectionwith said metal sleeve; and removing said mandrel.
 2. A method accordingto claim 1, wherein said first-named applying step includes coveringrecesses in the form of longitudinally extending, circumferentiallyspaced grooves on the outer periphery of said sleeve.
 3. A methodaccording to claim 2, wherein said first-named applying step includescovering ribs disposed between said grooves, said ribs increasing inthickness in a direction away from the adjacent end of the shaft topresent an inclined outer face.
 4. A method according to claim 1,wherein said arranging step includes positioning a plurality ofarc-shaped segments around said previously applied fibrous material,said pressing members comprising tongues extending radially inwardlyfrom said segments.
 5. A method according to claim 4, wherein saidsegments are arranged in circumferential end-to-end fashion to form a360 degree cylinder.
 6. A method according to claim 1, wherein saidfirst-named applying step comprises applying a single layer of fibrousmaterial prior to said pressing step.
 7. A method according to claim 1,wherein said applying step includes applying a plurality of layers orfibrous material prior to said pressing step.
 8. A method of forming atubular reinforced composite drive shaft comprising the stepsof:positioning a metal sleeve having longitudinally extending,circumferentially spaced grooves upon the outer periphery thereof upon asegment of a mandrel; applying fibrous material bearing a non-solidifiedresinous material upon said mandrel and over said grooves in saidsleeve; arranging a plurality of pressing members in radially inwardlypressing relationship with said previously applied fibrous material andin overlying relation to said grooves to press portions of said fibrousmaterial into said grooves while bearing said non-solidified resinousmaterial thereon; applying additional fibrous material bearing saidnon-solidified resinous material to said previously applied fibrousmaterial and said tongues to retain said tongues in position;solidifying said resinous material with portions of said previouslyapplied fibrous material being positioned in said grooves to create atorsion-transmitting connection with said metal sleeve; and removingsaid mandrel.
 9. A method according to claim 8, wherein said first-namedapplying step includes covering ribs disposed between said grooves, saidribs increasing in thickness in a direction away from the adjacent endof the shaft to present an inclined outer face.
 10. A method accordingto claim 8, wherein said arranging step comprises positioning aplurality of arc-shaped segments in circumferential end-to-end fashionto form a 360 degree cylinder, said pressing members comprising tonguesextending from said segments.
 11. A method according to claim 8, whereinsaid first-named applying step comprises applying a single layer offibrous material prior to said pressing step.
 12. A method according toclaim 8, wherein said first-named applying step comprises a plurality oflayers of fibrous material prior to said pressing step.